Method for forming a container from bi-axially orientable plastics material and having an integral handle

ABSTRACT

A method of forming a container from bi-axially orientable plastics material and having an integral handle with the steps of forming a preform having a neck portion and an expandable portion below the neck portion, with the neck portion including a locating ring above the expandable portion and a handle molded to the non expandable at one end and molded to the expandle portion at the other end. Where the molded-in handle is the approximate length of the handle of the finished container. The unblown preform of orientable plastics is inserted into a blow molder and thereafter stretched by a stretch rod. During the stretch process the handle on the preform unbends rather than stretching to form the approximate shape of the handle in the finished container. The blow mold then closes on the stretched preform thus capturing the handle. Blow gas is then injected into the interior.

RELATED APPLICATION

This is a non-provisional application claiming the priority date ofProvisional Application No. 61/242,898 filed Sep. 16, 2009.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a method for forming a container frombi-axially orientable plastics material and having an integral handleand in more particular using PET or like thermoplastics material.

2. Description of Prior Art

There is a continuous demand, particularly in the food and beverageindustry, for articles, such as bottles, buckets, pitchers, etc., madeof clear, tough plastic because they are relatively inexpensive, easy touse, generally non-breakable and serve as good substitutes for glass. Itis oftentimes desirable that such articles have handles to as goodsubstitutes for glass. It is oftentimes desirable that such articleshave handles to aid in their use, particularly large bottles.

However, it is generally understood that PET lacks sufficient hot meltstrength to be extrusion blow molded and it work hardens therebypreventing it from entering shallow areas or forming sharp corners of amold which form an integral handle. As a result, integrally moldedhandles on PET bottles have been susceptible to breakage, especiallywhen molded in bottles of larger sizes. The bottle industry has soughtan integral-handled PET bottle since PET was first commerciallyavailable in 1977. Eastman, DuPont, and other PET resin manufacturersdeveloped a modified PET, called E-PET, that allowed the composition tobe extrusion blow molded to form bottles with handles for detergents,milk, etc. However, these bottles were not properly oriented andshattered when drop tested. Also, E-PET was costly and efficiencies inproduction could not be utilized to reduce the bottles' cost.

Thus, when PET was used and handles were desired, it had been thepractice to attach the handle to the PET article in a separateoperation, such as by ultrasonic fusion, after the blow molded PETarticle had been formed in, and removed from, the blow mold. U.S. Pat.No. 4,727,997 discloses a method and apparatus for producing a PETbottle with a PET handle. In a first step, a parison is blow molded in ablow mold which has inwardly extending circumferential ridges to producea blown bottle with article-encircling grooves therein. In a secondstep, the blow molded bottle is transferred to a second grip formingmold, which has circumferential grooves therein, and a handle isinjection molded onto the bottle.

Another approach has been to injection mold a thermoplastic handle in aseparate operation from the blow molding of the container, and then tosnap the separately molded handle over the neck or finish of the blownPET bottle. In accordance with a still further proposal, the separatelymolded handle is inserted into the blow mold and the bottle is blownover, or into, the handle. This rests in a bottle that has a carryinghandle or a two handed pour bottle.

Others have previously attempted to overcome the problems associatedwith forming PET bottles with durable integral handles. U.S. Pat. Nos.4,992,230, 4,993,931 and 5,057,266 all disclose a method and apparatusfor making a hollow blow molded PET article with an integral externalprojection such as a handle. The method includes blow molding the hollowarticle and then injection molding the integral projection thereon. Theapparatus includes a combination mold having separate and independentblow mold and injection mold cavities which communicate at an interfacetherebetween. In essence, in the method and apparatus of that invention,a PET preform is inserted into a combination blow mold and injectionmold wherein the blow mold cavity defines article (bottle) to be blownand the injection mold cavity defines the handle. The blow mold andinjection mold cavities are in communication with each other at alocation defining the area where the handle is to extend from thecontainer. After insertion into the blow mold, the preform is injectedwith blow gas from a gas nozzle to conform the preform to the blow moldcavity thereby forming the hollow blow molded bottle. While the pressureof the blow gas holds the preform in conformity with the blow moldcavity, and prior to exhausting the blow gas, molten PET is injectedunder pressure into the injection mold cavity to form the integralhandle and bond it to the blown preform bottle at the point where theinjection mold cavity communicates with the blow mold cavity. Thecombination mold is then opened and the finished bottle is removed.

Another attempt to solve the handle problem U.S. Pat. No. 6,733,716whereby a PET bottle is stretch blown and the heated mold parts close onthe blown bottle and try to form a handle. With this method materialmust then be trimmed out causing wasted and decrease production rates.

None of the above practices, however, has been entirely satisfactory inmaking PET bottles with integral handles since they add steps to thefabrication process, utilize extra materials, and employ complicatedmolds. Furthermore, other known methods requiring ultrasonic bondingequipment or multiple separate molds are unduly time-consuming,unnecessarily expensive and still do not overcome the handle breakageproblem seen in larger bottles or containers.

There is still room for improvement in the art.

SUMMARY OF THE INVENTION

The current invention is a method of forming a container from bi-axiallyorientable plastics material and having an integral handle with themethod of forming a preform having a neck portion and an expandableportion below the neck portion, said neck portion including a locatingring above the expandable portion and a handle molded to the nonexpandable at one end and molded to the expanded portion at the otherend. The molded-in handle is the approximate length of the handle of thefinished container. The unblown preform of orientable plastics isinserted into a blow molder and thereafter stretched by a stretch rod.During the stretch process the handle on the preform unbends rather thanstretching to form the approximate shape of the handle in the finishedcontainer. The blow mold then closes on the stetched preform thuscapturing the handle. Blow gas is then injected into the interior of thepreform. The blow gas causes the handle portion of mold to move to theshape of the finished container while simultaneously blowing thefinished container. After the preform is blown into the shape of thebottle in the mold, blow gas is discharged from the stretch rod.

BRIEF DESCRIPTION OF DRAWINGS

Without restricting the full scope of this invention, the preferred formof this invention is illustrated in the following drawings:

FIG. 1 a shows the preform prior to being blown;

FIG. 1 b shows a side view of the preform prior to being blown;

FIG. 1 c shows a cross section of the preform prior to being blown;

FIG. 1 d shows a cross section of the handle;

FIG. 2 shows a schematic of the preform in the stretched position withan adjustable stretch rod in the blowmold with the moveable handlepiece; and

FIG. 3 shows a schematic of the blown bottle in the mold with themoveable handle piece shifted to it final position.

DETAILED DESCRIPTION

The following description is demonstrative in nature and is not intendedto limit the scope of the invention or its application of uses.

There are a number of significant design features and improvementsincorporated within the invention.

The current invention is a method of forming a container 100 frombi-axially orientable plastics material and having an integral handle 10with the method of forming from a preform 1.

According to one aspect of the invention, there is provided a preform 1for a container 100 comprised of orientable thermoplastic material andarranged so that the resultant blown container 100 will include a handle10 with the preform 1 comprising a molded structure having a neckportion 20 and an expandable portion below the neck as shown in FIGS. 1a and 1 b. The preform 1 will have an opening 30 and cavity 40 as shownin the cross section view of FIG. 1 c with a handle cross section 12.

The neck 20 typically includes a locating ring above the expandableportion as shown in a cross section in FIG. 1 d. The preform has anintegrally molded solid handle attached at 2 points along the verticalaxis. The first point of attachment can be either at the non expandableportion of the preform or the expandable portion of the preform. Thesecond point of attachment is at the expandable portion of the preform.The approximate length of the desired handle in the finished container100 determines the length of the handle. Therefore the shape of theattached handle can be of various geometries to accommodate the desiredhandle length.

During the blow molding operation the preform 1 is oriented in a mannerto provide sufficient heat behind the handle 10 while not overheatingthe handle 10. On the final station prior to blowing the container 100the preform 1 is oriented so that the handle 10 is in the properalignment with mold 70. In a typical injection stretch process the mold70 would close, the stretch rod 60 would be extended and the blow airwould create the container. Unlike typical injection stretch blownprocesses when the preform 1 arrives at the blowing station the neck 20of the preform 1 is externally secured. The modified stretch rod 60 isextended causing the preform to stretch.

The modified stretch rod 60 may have an adjustment portion 65 to adjustthe size of the rod 60.

When the preform 1 stretches, the attachment points of the handle 10become separated to the distance of the blown container. The handle 20itself does not stretch rather uncoils. This causes a sufficient gapbetween the preform 1 and the handle 20. The mold then closes and thehandle 20 is then trapped in the handle pocket 80 of the mold. Thehandle pocket 80 of the mold 70 is allowed to move to its final locationby means of the blow air while the container 100 is blown. The movablemold segments within the blow mold cavity may be unitary segments or maythemselves consist of multiple parts. When the mold 70 is opened thehandle pocket 80 is retracted resulting in an injection stretch blowncontainer with an integral handle attached at 2 points.

In an alternate version of the preform, the preform handle could beachieved by mechanical means by physically attaching the handle to thepreform outside the injection molding process or by coinjecting thehandle on the preform.

In an alternate version of the preform, the preform could be molded witha handle that is shorter than the finished handle. The handle 10 itselfcould be stretched to the desired length with the stretch rod 60.

In an alternate form of this invention utilizing the handled preform 1the sequence of the injection stretch operations could be modified. Whenthe oriented preform is sequenced into the molding station the molds 70would close, the stretch rod 60 would be extended. However prior toblowing the container 100, the handle pockets in the mold 70 wouldextend to capture the handle 20. When the container 100 is blown thehandle pocket would be allowed to move to the finished containerrequirements. The movable mold segments within the blow mold cavity maybe unitary segments or may themselves consist of multiple parts.

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible. Therefore, the point and scope of the appended claims shouldnot be limited to the description of the preferred versions containedherein.

As to a further discussion of the manner of usage and operation of thepresent invention, the same should be apparent from the abovedescription. Accordingly, no further discussion relating to the mannerof usage and operation will be provided.

What is claimed is:
 1. A method of making a hollow blow molded articlefrom a preform of thermoplastic polymer, the preform having an interiorcavity, an exterior wall, a neck portion and a handle attached to theexterior wall at two points and extending from the exterior wall in acoiled configuration, the method comprising: inserting the preform intoa blow mold having a hollow article-defining blow mold cavity andmovable mold segments; orienting the preform in a manner to providesufficient heat behind the handle while not overheating the handle;reorienting the preform prior to blowing the container so that thehandle is in a proper alignment with the blow mold; securing the neckportion; extending a modified stretch rod within the internal cavity,causing the preform to stretch such that a distance between theattachment points of the handle increases by an amount sufficient touncoil the handle while leaving a sufficient gap between the preform andthe handle and without stretching the handle; closing the mold causingthe handle to be trapped by a movable handle pocket of the blow mold inan initial position; supplying blow air to the interior cavity, causingthe preform to inflate and causing the movable handle pocket to move toa finished position of the hollow blow molded article; opening the blowmold; and removing the blow molded article, allowing the movable handlepocket to retract to the initial position.
 2. The method of claim 1,wherein the stretch rod makes contact with the preform during stretchingat two discrete points, the first point being at a bottom portion of thepreform and the second point being at an interior portion of the preformproximate the point of attachment of the handle furthest from the neckportion.
 3. The method of claim 1, wherein the movable handle pocketcomprises multiple parts.
 4. The method of claim 1 wherein, prior tosupplying blow air to the internal cavity, the movable handle pocketextends to capture the handle.